Vacuum actuated ignition timing device



Feb. 20, 1962 R. K. FRANK VACUUM ACIUATED IGNITION TIMING DEVICE 2Sheets-Sheet 1 Filed Feb. 16, 1961 INVENTOR.

www@ C Arrow/Ey Feb. 20, 1962 R. K. FRANK 3,021,828

VACUUM ACTUATED IGNITION TIMING DEVICE A Trop/Vey @AMQMIM nauw iinitetats This invention relates generally to ignition distributors forinternal combustion engines, and more specifically to thoseignitiondistributors -wherein theA advance mechanism is controlled inaccordance with engine manifold and carburetor venturi vacuums, commonlyreferred -to as full pressure distributors.

It is generally agreed that greater fuel economy and improved engineperformance can-be obtained by increasing the degree of ignition advanceover that presently obtainable during periods of part throttle engineAoperation. However, this has not been possible with knownconstructions.

Full pressure distributors usually employ a flexible diaphragm, which issecured to a movable breaker plate and positioned by both the enginemanifold vacuum and venturi vacuum. Springs are also provided forpurposes of calibration by resisting the movement of the diaphragm. As aresult of this general arrangement, it becomes obvious that the springrate isa controlling factor regardless of which ever vacuum is theactuating force; that is, manifold or Venturi vacuum. Consequently, thesprings which establish the wide-open-throttle (W.O.T.)

advance curve also serve to limit the part throttle advance curve.

Accordingly, the object of this invention is to provide meansestablishing the desired W.O.T. advance, but at the same time allowinggreaterrignition advances during part throttle engine operation.

Other objects and advantages will become more apparent when reference ismade to the following written description and the attached drawingswherein:

FIGURE l is a fragmentary cross-sectional view of a carburetorconstructed generally in accordance with the teachings of the inventionand cooperating with an ignition distributor;

FIGURE 2 is a graph illustrating the road load part throttle and wideopen throttle ignition advance curves of a conventional ignition system;

FIGURE 3 is a graph illustrating the road load part y I throttle andwide open throttle ignition advance curves for an ignition systemconstructed in accordance with the teachings of the invention.

Referring now in greater detail to the drawings, FIGURE 1 illustrates alcarburetor 1G having an induction passage 12 with a throttle valve 14therein controlling the ow therethrough to the intake manifold 16 of theengine. An actuating lever 1S may be suitably secured to the throttleshaft 22, and a rod 20 and spring 24 may be provided to cooperate withlever 1S for positioning the throttle valve 14.

The ignition distributor 26 may be comprised generally of a housing 28having provision therein for the reception of a driving shaft to which acam 36 is secured so as to rotate therewith. A breaker plate 32 mountedon a suitable bearing member is adapted to rotate about the drivingshaft and cam 30. Thek breaker plate 32 carries thereon a breaker armassembly 34 which includes a cam engaging portion 36 engage'able by therotating cam 30 The distributor advance mechanism is controlledgenerally by the pressure responsive device 40 which communicates bymeans of suitably conduitry with ports 42 and 44 in the carburetor 10 soas to sense engine manifold and carburetor venturi vacuum, respectively.

The pressure responsive device 40 may be substantially comprised of ahousing 46 and a cover member 48 rigidly held together in a manner so asto peripherally Secure a diaphragm member 50 therebetween. A member 52,connected at its one end to the diaphragm member 50, isadapted to beoperatively engaged with the breaker plate 32, as by means of a holeformed therein for the reception of the end 54 of member 52. Anysuitable retaining means such as a cotter pin 56 may be employed so asto prevent accidental disengagement between member 52 andbreaker plate32. Chamber. 58 formed generally by cover 48 and diaphragm 50 is exposedto va 'source of vacuum, while the chamber 60` is vented to theatmosphere.

The entire pressure responsive device 40 may, of course, be secured tothe housing 28 by any suitable means such as screws 62.

Calibrating springs 64 and 66 are secured at one end to the anchor pins68and 70, which in turn are xedly secured to the housing 28. The otherends of springs 64 and 66 are connected to the breaker plate springposts 72 and '74. Openings 76 and 78 may of course be formed in thebreaker plate `32 in order to provide the necessary clearance for anchorpins 68 and '70.

Other portions of the distributor such as the distributing rotor, upperdistributor cap and various output terminals are neithersh'own nordescribed, since they form no part of this invention and are well knownto those skilled in 4the art.

Valving means illustrated generally at 8i); are provided in order tomodify the vacuum which is ultimately communicated to chamber 58. Thevalving means are comprised generally of two independently actuatedvalve assemblies 82 and 84', which may be contained within the generalstructure of the carburetor body 11 if so desired.

Chambers S6 and 88 formed generally within the body 11 at timescommunicate with each other by means of an orifice controlled by a valvemember 92. A spring 94 normally urges the valve member 92 to the left,thereby maintaining the orice 90 closed. The throttle shaft 22 may havea cam-like surface 96 formed thereon which will, at appropriate times,engage the end 98 of valve lmember 92 and urge '1t to the right againstthe force of spring 94, thereby opening orifice 90 and allowingcommunication between chambers 86 and 8S. A conduit 160, communicatingwith chamber 86, has its other end terminating in a port 102 posteriorto the throttle valve 14 when the latter is in its normally closedposition.

Valve assembly 84, which may be threadably received Within the chamber88, is comprised of a housing portion 104 which cooperates with a covermember 106 to perpherally secure a pressure responsive diaphragm member108 therebetween. Chamber 110, formed generally by the diaphragm 108 andcover 106 is vented to the atmosphere, as by ports 112, while chamber114 on the opposite side of the diaphragm is in communication with theinduction passage 12 by means of port 42, conduit 116 and radiallyformed passages 118 in the housing 104.

An orifice 120 formed in housing 104 provides communication at timesbetween chambers 88 and 114, depending upon the position of the valvemember 122. The valve member 122 has -its one end 124 connected to thediaphragm108 so as to bemoved therewith. Springs 126 and 123 andIadjustment. member 130 are, of course, provided so as to enableselection of the particular vacuum value at which valve member 122 willbe moved to the right and orifice 1.20 will be opened. A conduit 132,including a restriction 134 therein, communicates between apanage 3 ichamber 8S and conduit 136 Whichleads from port-44 to chamber 5S of thepressure responsive device 44%.

Operation Referring to FrGURE 1, let it be assumed' that the engine isrunning at Vcurb idle andthe spark advance mechanism is in full retard.Under these conditions, the ele'- V.ments would assume positions asillustrated in FIGURE l'.

Springs 64 and 66, being anchored at one end to the housing 28 by meansof anchor pins 68 and 7i), respectively, and connected at theirrespective other'ends to the 'breaker plate spring posts 72 and 74, urgethe breaker plate 32 clockwise about the distributor shaft and cam 30until the holes 108 'andrll forr'ned in theplat'e 32 abut against theanchor pinsj68 and 70. This causes the breaker arm assembly 34 to berotated to a position whereby the cani 30 will contact the can engagingportion 36 at a .time when the respective pistons within the engine aremostnearly at 'top dead center.

If the throttle valve 14 is moved to wide open position, the air 'owpast 'the venturi 138 'causes a venturi vacuum at port 44 which isdirected generally by means of conduit 136 to chamber 5S. Asengine speedincreases' 'with the throttle valve maintained at wide open position,the venturi vacuum increases, causing the diaphragm 50 to be moved inever increasing lamounts to the left thereby rtating the breaker plate32 and the breaker arm assembly counter-clockwise about cam 30. This inturn causes the cam 30 to engage the cam engaging portion 36 at everincreasing degrees of engine crankshaft rotation ahead of when theengine pistons reach top dead center. This is usually referred to bythose skilled in the art as degrees of' ignition advance and isillustrated by curve 140 or FlG- URE 2.

It should be noted that during this period of wide open throttleoperation, the throttle shaft 22, by virtue of the action of its camportion 96 during the last few degrees of movement towards wide openthrottle position, has moved valve member 92 to the right so as to openorice 90. As a consequence of this, conduit 132 is in communication withconduit 160 and port 102 which are at substantially atmosphericpressure. This results in a bleeding effect through restriction 134,causing a diminution of the venturi vacuum as sensed by diaphragm Stiand continuing to do so whenever the valve member 92 has opened orifice90.

In view of the above, it becomes apparent that lighter Calibratingsprings 64 and 66 may be employed; this is because the effective forceopposing them and created by the venturi vacuum has been materiallydiminished by causing o'rice 90 to be opened so as to allow atmosphericpressure to bleed oit the venturi vacuum.

lf, for example, the throttle valve were opened slowly from its fullyclosed position to some part throttle position as required by normalroad loads, the valve 92 would remain in its closed position and port d2would be exposed to manifold vacuum.

The existing manifold vacuum would then be communicated by means ofconduits lio and 11S to chamber li, causing the diaphragm 108 and valve122 to move to the left. Since, as stated previously, the valve 92 isclosed, the manifold vacuum is directed past restriction 134 to chamber$8 causing an increase in ignition advance. As a result of the provisionof lighter or weaker Calibrating springs, there is less resistanceotiered to the movement of the diaphragm 59, and consequently greaterignition advances at part throttle engine operating conditions isobtainable than with prior conventional ignition systems.

The graphs of FIGURES 2 and 3 are presented to illustrate thecomparative advautageof the invention over that of conventionaldistributors. While curves i4@ and L52 of FlGURES 2 and 3, respectively,are identical to each other; it can be seen from curve 144 that theinvention provides for much greater ignition advance duringY partthrottle engine operation".

To this point, the construction and operation of the invention have beendescribed without reference to passage 1148 and it is apparent that theinvention is operative Without passage 148, which was included in FIGUREl as a convenient way of disclosing a `second embodiment.

Therefore, as'an alternate construction to that already describedracalibrated passage lil-i8 may be provided within the body member of 104so as to continually communicate a small degree of manifold vacuum toconduit i312. during those periods of engine operation wherein themanifold vacuum as yet is insuhcient to fully open valve 122 against theaction o spring 12S. The basic operation of the entire invention isstill the same; the primary distinction is that in the -absence of acalibrated bypass such as passage 1418, no communication of manifoldvacuum from port 42 4to conduit l13.2 is possible until vthatpredetermined value of manifold vacuum is attained which will completelyopen valve 122.

FlGURE 3 illustrates the ee'ct of providing such a calibrated bypasspassage as 148. That is, the advance curves for manifold vacuum valuesof 2, 4 and 6 inches of Hg are separated from veach other by arelatively small increment. This is a direct result of the calibratedpassage 14S because even though the passage is restrictive in nature, itnevertheless continually conveys a portion of the then existing manifoldvacuum.

if the calibrated passage 148 were not provided, the ad- Vance curvesfor manifold vacuum values of 2, 4 and 6 inches of Hg would all fall onone curve, possibly on the two inch curve. This is, of course, assumingthat the predetermined vacuum value for actuating the diaphragm 16S-iseight inches of manifold vacuum,

Accordingly, it can be seen that in addition to providing greaterignition advance during periods of road load conditions, the inventionalso serves to lower the ignition advance curves for conditions of 2, 4and 6 inches of Hg manifold vacuum, while still raising the curves forconditions such as 8, lO and l2 inches of 'Hg manifold vacuum. 4Theparticular values can of course be selected by proper selection andcalibrationof valve 84. Consequently, the ignition advance curves can becontrolled so `as to avoid any particular area characteristic to theengine wherein undesirable detonation occurs. v

Although but two embodiments of the invention have been disclosed anddescribed, it is apparent that other 'modifications of the invention arepossible within the scope or the appended claims. 1

Whatl claim as my' invention is:

1. Anignition system for an internal combustion engine having aninduction passage with a throttle valve controlling the ow of airtherethrough; comprising an ignition distributor having a housing, aswitch in said housing, a ca-rn member normally rotatable in accordancewith engine speed and adapted to intermittently open said switch foreffecting a make and break of the ignition circuit, a breaker platenormally supporting said switchA and having relative angular motion withrespect to said housing; pres'- sure responsive` means secured to saidhousing and operatively connected to said breaker plate for rotatingsaid breaker plate in accordance with yengine requirements; a venturiformed in said induction passage upstream of said throttle valve; trstconduit means communicating between the throat of said venturi and saidpressure responsive means; second conduit means communicating betweensaid induction passage at a point upstream of said throttle Valve whensaid throttle valve is in its normally closed position and said rstconduit means; first valve means connected serially in said secondVconduit means adapted to at times control the communication through saidsec- 'ond conduit means; said iirst valve means comprising a diaphragmmember, a valve member secured to said diaphram member and adapted to bepositioned thereby, said diaphragm member being responsive Vto thevacuum sensed by said second' conduit means at vits point ofcommunication with said induction passage and etective'to move said Stivalve member in the opening direction upon the attainment of apredetermined vacuum valve; third conduit means communicating betweensaid induction passage at a point downstream of said throttle valve whensaid throttle valve is in a substantially closed position and saidsecond conduit means on the iirst conduit means side of said iirst valvemeans; second valve means connected serially in said third conduit meansadapted to control the communication of said third conduit means withsaid second conduit means; and a cam member rotatably positioned inaccordance with the position of said throttle valve and adapted to attimes abut against and urge said second valve means in the openingdirection so as to allow complete communication between said second andthird conduit means.

2. An ignition system for an internal combustion engine having aninduction passage with a throttle valve controlling the ow of airtherethrough; comprising an ignition distributor having a housing, aswitch in said housing, a cam member normally rotatable in accordancewith engine speed and adapted to intermittently open said switch foreffecting a make and break of the ignition circuit, a breaker platenormally'suppo-rting said switch and having relative angular motion withrespect to said housing; pressure responsive means secured to saidhousing and operatively connected to said breaker plate for rotatingsaid breaker plate in accordance with engine requirements; a venturiformed in said induction passage upstream of said throttle valve; rstconduit means communicating between the throat of said venturi and saidpressure responsive means; second conduit means communicating betweensaid induction passage at a point upstream of said throttle valve whensaid throttle valve is in its normally closed position and said rstconduit means; first valve means connected serially in said secondconduit means adapted to at times control the communication through saidsecond conduit means; said rst valve means cornprising a second pressureresponsive member, a valve member secured to said second pressureresponsive member and adapted to be positioned thereby, said secondpressure responsive member being responsive to the vacuum sensed by saidsecond conduit means at its point of communication with said inductionpassage and effective to move said valve member in the opening directionupon the attainment of a predetermined vacuum value; third conduit meanscommunicating between said induction passage at a point downstream ofsaid throttle valve when said throttle valve is in a substantiallyclosed position and said second conduit means on the first conduit meansside of said first valve means; and second valve means connectedserially in said third conduit means adapted to allow completecommunication of said third conduit means with said second conduit meanswhenever said throttle valve is in a substantially wide open position.

3. An ignition system for an internal combustion engine having aninduction passage with a throttle valve controlling the tlow of iairtherethrough; comprising a throttle shaft; an ignition distributorhaving a housing, a switch in said housing, a cam member normallyrotatable in accordance with engine speed and adapted to intermittentlyopen said switch for effecting a make and break of the ignition circuit,a breaker plate normally supporting said switch and having relativeangular motion with respect to said housing; pressure responsive meanssecured t-o said housing and operatively connected to said breaker platefor rotating said breaker plate in accordance with engine requirements;a venturi formed in said induction passage upstream of said throttlevalve; first conduit means including a first restriction thereincommunicating between the throat of said venturi and said pressureresponsive means; second conduit means including a second restrictiontherein communicating between said induction passage at a point upstreamof said throttle valve when said throttle valve is in its normallyclosed position and said rst conduit means at a point between said firstrestriction and said pressure responsive means; rst valve meansconnected serially in said second conduit means adapted to at timescontrol the communication through said second conduit means; said lirstvalve means comprising a main body portion, a cover member, a diaphragmmember, a valve member secured to said diaphragm member and adapted tobe positioned thereby, a passageway Iformed through said main bodyportion providing a valve oriiice adapted to cooperate with said valvemember for controlling the transmission of vacuum therethrough, andspring means normally urging said diaphragm member in a direction so asto move said valve member in the closing direction, said diaphragmmember being responsive to the vacuum sensed by said second conduitmeans at its point of communication with said induction passage andetective to move said valve member in the opening direction against theforce of said spring means upon the attainment of a predetermined vacuumvalue; third conduit means communicating between said induction passageat a point downstream of said throttle valve when said throttle valve isin a substantially closed position and said second conduit means on theirst conduit means side of said first valve means; second valve meansconnected serially in said third conduit means adapted to control thecommunication of said third conduit means with said second conduitmeans; and a cam member rotatable with said throttle shaft and adaptedto at times abut against and urge said second Valve means in the openingdirection so as to allow complete communic-ation between said second andthird conduit means.

References Cited in the tile of this patent UNITED STATES PATENTS2,381,610 Mallory Aug. 7, 1945 2,475,717 Ostling July 12, 1949 2,867,197McCollough Ian. 6, 1959

